Bridgeport Lake Private Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Bridgeport Lake Private Observatory clear sky chart from 2005-11-06 to 2024-01-16.

This page is a summary of past forecasts. Even though it's based only on forecasts, some people use these pages as clue to a site's climate. But climate data based on actual observation should be preferred (if you can find it!).

Cloud, Transparency and Seeing forecasts are summarized individually. But because good observing conditions require a combination of minimum cloud cover, transparency and seeing, the individual forecast summaries can be difficult to interpret. The observing conditions section counts the combinations of conditions needed for common types of astronomical observation.

Observing Conditions

The following tables count the occurrence of the combinations of forecast and darkness conditions needed for different observations. Conditions are rated by by what percentage of the hours the observation would likely be attempted are usable.
Observation TypeMinimum conditions for hour to be usableOut of hours
Clear of CloudsTransparencySeeingSky Brightness
Planetary:50%(no limit)Average(no limit)Nighttime Hours
Deep Sky:70%Average(no limit)5.9Nighttime Hours
CCD Imaging:70%Below AveragePoor(no limit)Nighttime Hours

Percentages are of nighttime hours per month, or per year, when a particular observing conditions was met. Deep Sky percentages never exceed 50% because the moon is up half the time. Deep sky percentages are much lower for charts at high latitudes because of fewer dark hours in the summer.

Overall

PlanetaryData
Pts
Deep Sky
Max 60%
Data
Pts
Both Planetary and Deep Sky
Max 60%
Data
Pts
Either Planetary or Deep SkyData
Pts
CCD ImagingData
Pts
Night
59%
23515
31%
74622
24%
23480
68%
23480
47%
35897

By Month

MonthDays of MonthPlanetaryData
Pts
Deep Sky
Max 60%
Data
Pts
Both Planetary and Deep Sky
Max 60%
Data
Pts
Either Planetary or Deep SkyData
Pts
CCD ImagingData
Pts
January1st to 10thNight
47%
756
27%
2646
17%
756
62%
756
38%
1306
January11th to 20thNight
56%
744
25%
2568
21%
744
66%
744
41%
1225
January21st to endNight
53%
792
31%
2574
26%
792
62%
792
37%
1361
February1st to 10thNight
53%
720
30%
2264
25%
720
64%
720
41%
1152
February11th to 20thNight
52%
700
32%
2099
24%
700
64%
700
46%
1043
February21st to endNight
46%
592
31%
1776
20%
592
61%
592
43%
912
March1st to 10thNight
43%
720
24%
2160
16%
720
55%
720
38%
1156
March11th to 20thNight
50%
720
25%
2056
18%
720
59%
720
44%
1067
March21st to endNight
42%
792
25%
2008
10%
792
53%
792
45%
1129
April1st to 10thNight
49%
720
26%
1800
11%
720
58%
720
43%
1031
April11th to 20thNight
49%
711
28%
1779
12%
711
56%
711
47%
978
April21st to endNight
53%
720
28%
1800
11%
720
60%
720
52%
955
May1st to 10thNight
50%
599
29%
1679
17%
599
56%
599
45%
880
May11th to 20thNight
57%
493
30%
1556
23%
493
63%
493
48%
723
May21st to endNight
59%
388
26%
1552
24%
388
68%
388
35%
740
June1st to 10thNight
64%
360
30%
1440
29%
360
76%
360
45%
597
June11th to 20thNight
67%
360
36%
1440
37%
360
80%
360
62%
496
June21st to endNight
70%
360
34%
1440
36%
360
81%
360
59%
520
July1st to 10thNight
83%
350
36%
1400
43%
350
89%
350
67%
469
July11th to 20thNight
77%
348
34%
1392
41%
348
81%
348
51%
549
July21st to endNight
82%
438
37%
1530
40%
414
83%
414
46%
687
August1st to 10thNight
76%
633
34%
1698
24%
630
78%
630
62%
827
August11th to 20thNight
77%
712
36%
1780
20%
712
80%
712
70%
851
August21st to endNight
78%
792
42%
1980
25%
792
80%
792
74%
922
September1st to 10thNight
78%
720
44%
1800
28%
720
83%
720
77%
821
September11th to 20thNight
73%
720
43%
1862
30%
720
79%
720
66%
888
September21st to endNight
69%
720
43%
1980
32%
720
79%
720
67%
897
October1st to 10thNight
66%
720
35%
2065
27%
720
77%
720
57%
984
October11th to 20thNight
71%
720
40%
2160
38%
720
79%
720
63%
932
October21st to endNight
66%
792
42%
2438
36%
792
78%
792
61%
1038
November1st to 10thNight
63%
740
34%
2405
30%
740
73%
740
53%
1069
November11th to 20thNight
59%
760
35%
2470
28%
760
72%
760
52%
1098
November21st to endNight
57%
760
35%
2470
28%
760
69%
760
50%
1128
December1st to 10thNight
51%
760
27%
2612
21%
760
62%
760
41%
1258
December11th to 20thNight
49%
759
25%
3184
21%
758
61%
758
28%
1677
December21st to endNight
42%
824
17%
4759
18%
817
55%
817
18%
2531

Individual Forecasts

The length of each colored bar in the "occurrence of each Forecast" column is proportional to the number of times the chart forecast that color. The percentages are of the total number of hours per month, or per year, with a particular forecast. The colors as the same as those used in clear sky charts.

Note: Transparency probabilities are only counted for those hours that have 30% or less cloud cover. Seeing probabilities are only counted for those hours that have 80% or less cloud cover. If that's too tricky, try Observing Conditions instead.

Overall

Occurrence of each ForecastData
Points
Cloud CoverDay
242442445%7%63%
74825
Night
132332345%7%66%
75002
TransparencyDay
20%6%10%20%25%19%
74532
Night
17%7%11%23%28%15%
74817
SeeingDay
7%15%26%29%17%5%
13980
Night
37%26%36%22%6%
23537

By Month

Percentage Cloud Cover SW (2006-)
Color Meanings:
Overcast 90% covered 80% covered 70% covered 60% covered 50% covered 40% covered 30% covered 20% covered 10% covered Clear
MonthDays in MonthOccurrence of each ForecastData
Points
January1st to 10thDay
12133346%6%12%58%
1519
11th to 20thDay
1214435%5%7%9%59%
1518
21st to endDay
26%34435%5%6%9%53%
1782
February1st to 10thDay
1325%42436%8%62%
1695
11th to 20thDay
1336%4345%7%10%55%
1750
21st to endDay
4145%345%6%8%59%
1480
March1st to 10thDay
1435%445%8%6%8%52%
1800
11th to 20thDay
1325%435%6%8%10%53%
1901
21st to endDay
14245%35%5%7%9%56%
2348
April1st to 10thDay
2434425%45%7%58%
2160
11th to 20thDay
142343445%7%63%
2129
21st to endDay
26%2332445%6%64%
2160
May1st to 10thDay
35%2443445%7%61%
2279
11th to 20thDay
3425%435%448%58%
2336
21st to endDay
5%7%36%4345%5%6%52%
2723
June1st to 10thDay
44145%345%5%7%59%
2520
11th to 20thDay
2112223345%74%
2520
21st to endDay
321332443470%
2520
July1st to 10thDay
3213324445%69%
2520
11th to 20thDay
4413323445%66%
2520
21st to endDay
6%42443445%6%59%
2692
August1st to 10thDay
4324424445%64%
2231
11th to 20thDay
3324423345%68%
2122
21st to endDay
331322233475%
2376
September1st to 10thDay
321332333373%
2160
11th to 20thDay
331332333471%
2098
21st to endDay
2212312245%76%
1980
October1st to 10thDay
3423323335%70%
1892
11th to 20thDay
3222213345%74%
1800
21st to endDay
122131235%6%74%
1915
November1st to 10thDay
132432345%6%67%
1674
11th to 20thDay
12122234410%69%
1710
21st to endDay
131242347%10%65%
1710
December1st to 10thDay
14233235%5%10%63%
1563
11th to 20thDay
26%36%5%36%7%6%9%47%
1928
21st to endDay
16%36%5%35%6%8%9%48%
2794
January1st to 10thNight
1425%4345%6%10%57%
2646
11th to 20thNight
313335%6%8%9%59%
2568
21st to endNight
25%35%4345%6%8%56%
2574
February1st to 10thNight
325%42445%8%62%
2264
11th to 20thNight
132442445%11%60%
2098
21st to endNight
1425%3235%7%8%61%
1776
March1st to 10thNight
5%25%5%246%7%9%55%
2160
11th to 20thNight
3333245%7%11%58%
2056
21st to endNight
1335%42445%8%62%
2008
April1st to 10thNight
2423325%46%9%60%
1800
11th to 20thNight
1424424446%66%
1779
21st to endNight
2423223445%70%
1800
May1st to 10thNight
241442345%8%64%
1679
11th to 20thNight
342332335%8%65%
1555
21st to endNight
35%1442435%6%63%
1552
June1st to 10thNight
5%21322445%7%67%
1440
11th to 20thNight
211111223482%
1440
21st to endNight
311221322280%
1440
July1st to 10thNight
111112246%80%
1440
11th to 20thNight
232332334474%
1440
21st to endNight
3313333445%68%
1620
August1st to 10thNight
221331333475%
1707
11th to 20thNight
212222335%78%
1780
21st to endNight
21122123482%
1980
September1st to 10thNight
111111222385%
1800
11th to 20thNight
121222223479%
1862
21st to endNight
231221224478%
1980
October1st to 10thNight
331231233474%
2065
11th to 20thNight
1212212246%77%
2160
21st to endNight
1112222246%76%
2438
November1st to 10thNight
1212223347%71%
2405
11th to 20thNight
122232335%7%71%
2470
21st to endNight
32331345%7%68%
2470
December1st to 10thNight
13243235%5%8%64%
2612
11th to 20thNight
1426%5%246%7%10%52%
3276
21st to endNight
16%36%6%46%7%7%10%45%
4862

Transparency (when cloud cover <= 30%)
Color Meanings:
Too cloudy to forecast Poor Below Average Average Above average Transparent
MonthDays in MonthOccurrence of each ForecastData
Points
January1st to 10thDay
18%9%19%28%19%6%
1519
11th to 20thDay
20%10%13%25%22%11%
1518
21st to endDay
26%9%13%21%23%8%
1782
February1st to 10thDay
19%7%13%25%24%12%
1695
11th to 20thDay
22%6%12%26%24%9%
1760
21st to endDay
21%8%15%27%24%6%
1480
March1st to 10thDay
25%7%18%23%20%7%
1800
11th to 20thDay
22%10%18%23%20%7%
1901
21st to endDay
21%9%21%30%15%5%
2348
April1st to 10thDay
24%8%16%25%18%8%
2160
11th to 20thDay
20%8%13%29%22%9%
2132
21st to endDay
20%7%16%30%22%6%
2160
May1st to 10thDay
21%5%10%30%26%7%
2279
11th to 20thDay
24%6%10%27%27%6%
2339
21st to endDay
30%7%11%22%24%6%
2724
June1st to 10thDay
23%7%9%21%30%10%
2520
11th to 20thDay
12%5%6%20%34%24%
2520
21st to endDay
17%4310%33%33%
2520
July1st to 10thDay
16%439%21%46%
2451
11th to 20thDay
20%5%411%20%41%
2445
21st to endDay
25%6%5%10%21%34%
2542
August1st to 10thDay
20%5%411%17%43%
2215
11th to 20thDay
18%439%27%39%
2122
21st to endDay
14%329%31%41%
2376
September1st to 10thDay
16%329%28%41%
2160
11th to 20thDay
15%4419%31%28%
2098
21st to endDay
13%3318%34%28%
1980
October1st to 10thDay
17%46%18%28%27%
1892
11th to 20thDay
14%45%22%32%24%
1800
21st to endDay
12%5%6%22%36%20%
1915
November1st to 10thDay
16%6%9%25%29%15%
1674
11th to 20thDay
12%6%11%26%33%12%
1710
21st to endDay
14%6%12%25%30%13%
1710
December1st to 10thDay
16%9%15%25%24%12%
1563
11th to 20thDay
30%12%13%20%17%8%
1928
21st to endDay
26%11%15%22%20%5%
2794
January1st to 10thNight
22%7%16%28%21%7%
2646
11th to 20thNight
17%9%17%25%22%10%
2568
21st to endNight
23%9%12%22%24%10%
2574
February1st to 10thNight
20%7%12%26%22%12%
2264
11th to 20thNight
20%5%11%29%27%8%
2099
21st to endNight
19%7%13%31%23%7%
1776
March1st to 10thNight
23%8%16%24%22%8%
2160
11th to 20thNight
18%7%18%26%22%7%
2056
21st to endNight
20%7%20%30%18%4
2008
April1st to 10thNight
20%9%15%31%18%7%
1800
11th to 20thNight
19%6%14%26%25%9%
1779
21st to endNight
17%6%15%36%23%3
1800
May1st to 10thNight
20%6%11%28%29%5%
1679
11th to 20thNight
18%411%34%27%5%
1556
21st to endNight
22%7%12%28%25%6%
1552
June1st to 10thNight
17%5%10%27%34%8%
1440
11th to 20thNight
9%37%20%38%23%
1440
21st to endNight
11%3416%32%34%
1440
July1st to 10thNight
7%4412%30%44%
1400
11th to 20thNight
13%6%413%28%37%
1392
21st to endNight
19%5%414%26%32%
1530
August1st to 10thNight
14%45%13%24%40%
1698
11th to 20thNight
10%4415%31%37%
1780
21st to endNight
8%3211%37%38%
1980
September1st to 10thNight
6%3213%36%40%
1800
11th to 20thNight
10%5%418%36%27%
1862
21st to endNight
11%3418%39%25%
1980
October1st to 10thNight
16%46%20%34%20%
2065
11th to 20thNight
11%36%23%36%20%
2160
21st to endNight
11%46%24%36%19%
2438
November1st to 10thNight
13%7%10%27%30%13%
2405
11th to 20thNight
13%7%11%26%33%10%
2470
21st to endNight
15%6%12%25%31%12%
2470
December1st to 10thNight
18%9%14%23%27%10%
2612
11th to 20thNight
25%11%15%23%21%5%
3276
21st to endNight
28%13%13%18%22%6%
4862

Seeing (when cloud cover <= 80%)
Color Meanings:
Too cloudy to forecast Bad 1/5 Poor 2/5 Average 3/5 Good 4/5 Excellent 5/5
MonthDays in MonthOccurrence of each ForecastData
Points
January1st to 10thDay
9%17%33%26%12%2
180
11th to 20thDay
419%28%25%17%7%
206
21st to endDay
6%14%24%34%17%5%
374
February1st to 10thDay
6%16%29%28%14%7%
374
11th to 20thDay
5%20%28%30%15%2
415
21st to endDay
7%21%30%27%13%2
346
March1st to 10thDay
5%19%36%29%9%3
420
11th to 20thDay
8%22%29%22%15%5%
420
21st to endDay
8%22%30%30%9%
462
April1st to 10thDay
10%20%30%26%11%2
420
11th to 20thDay
11%21%28%25%11%4
412
21st to endDay
10%20%25%25%14%6%
420
May1st to 10thDay
12%14%33%24%12%4
423
11th to 20thDay
14%21%25%22%12%6%
448
21st to endDay
13%18%20%24%19%7%
485
June1st to 10thDay
10%17%25%26%16%7%
450
11th to 20thDay
8%19%28%24%15%5%
450
21st to endDay
415%26%31%18%6%
450
July1st to 10thDay
411%25%33%19%8%
446
11th to 20thDay
5%8%22%33%25%7%
444
21st to endDay
8%7%21%35%21%8%
487
August1st to 10thDay
6%11%24%29%23%7%
447
11th to 20thDay
5%8%26%31%19%10%
437
21st to endDay
46%28%34%22%5%
495
September1st to 10thDay
5%9%23%36%19%8%
450
11th to 20thDay
7%15%23%30%20%4
450
21st to endDay
6%11%22%38%18%4
450
October1st to 10thDay
8%16%26%25%20%6%
450
11th to 20thDay
6%11%26%29%21%6%
450
21st to endDay
6%13%28%26%21%6%
430
November1st to 10thDay
5%13%26%26%21%9%
270
11th to 20thDay
410%25%26%24%10%
270
21st to endDay
311%24%31%24%6%
270
December1st to 10thDay
8%10%29%26%18%9%
201
11th to 20thDay
7%13%26%28%22%4
180
21st to endDay
9%18%29%26%14%5%
198
January1st to 10thNight
49%33%28%16%9%
760
11th to 20thNight
38%28%38%16%7%
744
21st to endNight
5%5%31%33%18%7%
792
February1st to 10thNight
38%29%35%20%5%
720
11th to 20thNight
38%31%32%19%6%
704
21st to endNight
411%33%35%12%4
592
March1st to 10thNight
410%37%32%13%5%
720
11th to 20thNight
412%30%30%18%7%
720
21st to endNight
312%37%31%14%2
792
April1st to 10thNight
5%9%32%35%16%3
720
11th to 20thNight
412%31%32%16%5%
711
21st to endNight
5%10%28%34%19%5%
720
May1st to 10thNight
6%9%31%33%17%5%
599
11th to 20thNight
5%7%26%36%23%3
493
21st to endNight
6%6%22%32%29%4
389
June1st to 10thNight
5%422%38%28%3
360
11th to 20thNight
3324%43%24%3
360
21st to endNight
3121%49%22%4
360
July1st to 10thNight
1112%51%31%4
350
11th to 20thNight
3211%52%31%2
348
21st to endNight
227%45%37%7%
438
August1st to 10thNight
3213%40%36%6%
633
11th to 20thNight
2214%42%33%6%
712
21st to endNight
3114%45%32%5%
792
September1st to 10thNight
1316%38%36%6%
720
11th to 20thNight
2318%42%29%7%
720
21st to endNight
3420%35%28%9%
720
October1st to 10thNight
35%22%39%25%7%
720
11th to 20thNight
36%15%41%27%7%
720
21st to endNight
35%23%31%26%12%
792
November1st to 10thNight
25%26%34%25%8%
740
11th to 20thNight
37%28%36%21%6%
760
21st to endNight
37%27%34%23%5%
760
December1st to 10thNight
37%34%34%17%6%
760
11th to 20thNight
38%34%34%17%4
760
21st to endNight
313%34%35%12%3
836
Page generated at 2024-01-13 16:28:32. Version ac07

Copyright 2024 Attilla Danko


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